A very popular way to leave a message is by writing down the words on a note paper. In a family life, it seems to be inconvenient to find a pen or a paper sheet for writing the message. Even a message is given on a paper, it will occur another problem, that is, where to locate the message and how to ensure the family member who will read the message clearly without missing the message?
It is therefore expected to invent a message lock by which anyone may leave message on a door lock for a convenient and safe messaging way.